This invention relates to radio frequency identification (RFID) systems and more particularly to a transponder of the system and the format of data in a response signal transmitted by the transponder forming part of the system.
RFID systems wherein a plurality of transponders are read by a reader, are well known in the art. In one known system, the reader broadcasts an interrogation signal. The transponders respond with respective response signals comprising transponder ID data. The response signals are received and the ID data read by the reader, thereby automatically to identify articles on which the transponders are mounted and/or to count those articles. Various protocols are known to avoid collisions between the respective response signals, or to mitigate the effect of signal corruption due to such collisions. Often the transponder ID data may comprise a plurality of blocks or pages of data, which pages are of equal length, typically 64 bits. In such systems, where a plurality of transponders are read simultaneously, it may be difficult for the reader to determine which page has been received from which transponder.